In the past few decades, the petroleum industry has invested heavily in the development of marine seismic survey techniques that yield knowledge of subterranean formations beneath a body of water in order to find and extract valuable mineral resources, such as oil. High-resolution seismic images of a subterranean formation are helpful for quantitative seismic interpretation and improved reservoir monitoring.
Permanent (hydrocarbon) reservoir monitoring (PRM) is a technique where multiple three-dimensional seismic “pictures” of the state of a hydrocarbon reservoir are taken such that a geologist or reservoir engineer may plan the location of additional boreholes for increasing the efficiency of the hydrocarbon extraction and/or may assess the efficiency of the current extraction techniques over time. In some cases, taking multiple seismic pictures of a hydrocarbon reservoir may be referred to as four-dimensional seismic.
For a typical PRM system, the system measures and records well performance and reservoir behavior from seismic sensors placed on the seafloor. Measurements are collected from permanently installed ocean bottom seismic cable systems.
A PRM system may utilize optical devices to sense parameters such as acceleration, motion and/or pressure, among others. For instance, optical devices can be used to sense seismic energy. The seismic energy may be naturally occurring, or may be imparted by a seismic energy source for the purpose of performing seismic surveys, geophysical exploration, and/or PRM, for example.
Marine-based PRM faces significant challenges that are not faced by land-based reservoir monitoring systems. This is particularly true of ocean bottom installations as water depths extend into the 1000 meter range and beyond. For purposes of seismic surveying, geophysical exploration, and/or PRM, cables may be retrieved or deployed using a pulley or capstan. Marine-based PRM equipment may therefore advantageously flex to conform to a capstan profile.